Adel Feizi, Peyman Bijanzad, Hadi Asfaram, Tahmasb Moazzenzadeh Khiavi, Mahdi Alimardan, Sasan Hamzei, Hojjat Ghabel and Saman Faramarzi
The prophylactic use of antibiotics in broiler feeds enhances growth rate and improved feed conversion ratio in poultry industry. In the European Union, the use of antibiotics for broilers has been limited to only antibiotics that are not used in human medicine. Therefore, in the last few years, uses of medicinal plants (essential oils) have been increased that because of their antimicrobial activity. This study was conducted to determine the effect of the addition of different levels of thyme, added to drinking water, on some hematological factors and Body weight gain (BW), feed conversion ratio (FCR), feed intake and mortality rate. Two hundred and forty, day-old broiler chicks (Ross-308) were divided into four equal groups (each group include 3 repetition). Experiment was as follow; a control group with no thyme and in other two groups, thyme extract was used 500 ppm and 1000 ppm and in last group feed was pellet and thyme was not used. Experiments were carried out for 42 days and thyme extract was used from day 7 to 42. Results showed that chicks fed with 1000 ppm thyme extract had significantly lower (p<0.05) feed intake, feed conversion ratio, and mortality rate followed by chicks fed with 500 ppm thyme extract and pellet group compared with control group, which showed the lowest performance. The highest BW was in pellet and 1000 ppm thyme group that was significantly different (p<0.05) from two other groups. Moreover, the chicks that get 500 and 1000 ppm thyme in drinking water had decreased (p<0.05) heterophils to lymphocyte ratio, this results showed that, increase of total bacterial count in other groups cause increase in heterophil numbers and due to that the heterophils to lymphocyte ratio increased in other groups and the highest increase was in pellet group which because of bacterial growth stress in that group. In conclusion, thyme extract could be considered as a potential natural growth promoter and have the advantage of inhibiting the growth of potential pathogens for poultry at the level of 1000 ppm.
